DIY EBS Catch Can… External Breather for the Street Glide…

Putting an external breather with a catch can on the Street Glide to catch a bit of the oil which collects in the air cleaner cover. I know this is really just treating a symptom and not really addressing the possible problem, but that is what I am looking to do right now. I plan to upgrade the cam chest at some point and when I do that I’ll replace the breather valves in the rocker boxes. For now this is just to keep some of the oil blow by out of my air cleaner and off the bike. Not expecting miracles, just hoping to keep things a little cleaner.

There are a few different external breather modification kits out there but I decided to DIY it and put together my own kit. Some of the kits are pretty nice but they come with a premium price tag, I was able to source everything I needed for less than $50… the hose barb connectors, the fuel line, and the drill/tap was around $15 (well $30 got me enough to DIY an EBS on 2 bikes). The catch can was about $35. This is about a third what the pre-assembled kits cost for a single bike. I could have saved a couple more dollars with brass fittings instead of stainless, but I liked the look of stainless over brass. Could have also saved a bit more money venting to atmosphere instead of a catch can, but I decided to go with a catch can.

Shopping list:

  1. Stainless Steel 1/4″ Hose Barb to 1/8″ Male NPT from Amazon – 5 in this pack so enough for 2 bikes.
  2. Stainless Steel 1/4″ Hose Barb 3 Way Tee from Amazon – 2 in this pack so enough for 2 bikes.
  3. 6 Feet 1/4″ ID Fuel Line from Amazon plenty for 2 bikes (dependent on how you route the lines)
  4. Drill and Tap Set for 1/8″ NPT from Amazon
  5. Vented Engine Motor Breather Canister V-Twin 40-0457 which I found on eBay but it also available on Amazon here.
  6. 3 oz Tube of Red High Temp RTV

I have the Screaming Eagle backing plate on the bike so it is going to require I drill and tap some holes in the back plate.

With the back plate still on the bike, I marked the location for the 1/8″ NPT hose barbs on the back plate. I did this a couple of times to make sure they were not going to be in the way of anything. I marked the location for the hose barbs using a bit of white paint on a small Phillips screw driver. Checked them again, and then again, and then removed the backing plate from the bike.

I used a center punch to mark the location and drilled out the holes using 3 drill bits: first a small one to get things started, then one that was about half the size of the final bit, and finally the “R” bit which came in the 1/8 NPT drill and tap set to get to the final size. The back plate is aluminum and was pretty easy to drill out, just take your time.
Drilling Back Plate for External Breather Catch Can
With the hole drilled I ran the tap in using a bit of WD40 to lubricate. It was pretty easy to cut the threads, just take your time.
1/8 NPT Threads Cut in Back Plate
The tap is tapered so it will get a bit harder to turn as it gets deeper. I ran the tap in until it was showing about 1/8″ inside the breather passage.

I threaded in the hose barbs, used some teflon tape to seal things up, and test fit everything. I cut the hose to length.
External Breather Hoses and Catch Can Mocked Up
When I was happy with how everything fit I removed the back plate to plug up the breather passages.

I used the RTV to plug up the passages from the breathers in the back plate.
Plugged Breather Holes in Back Plate Using RTV
It is a bit messy but should do the job. I let the RTV cure for 24 hours.

After the RTV cured I re-assembled the back plate, air filter, and air cleaner cover.
DIY External Breather with Catch Can
All buttoned up and ready to ride. Time will tell whether or not it makes a difference.

Since I have enough fittings and hose to do a second bike, I’ll probably pick up another catch can and add an external breather to the Wide Glide as well. I may get a piece of aluminum and see if I can turn my own catch can on the lathe – I think that would be a cool project.

Build. Tinker. Ride.

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